A variety of communication enabled devices may be employed by users for communications, business, and/or entertainment purposes. These devices may include, but are not limited to, mobile phones, stationary phones, personal digital assistants (PDAs), media players, desktop computers, laptop computers, tablet computers, handheld computers, inventory control handsets, point-of-sale terminals (POSs), set top boxes, and others. All of these devices may be referred to herein as user equipment (UE).
The session initiation protocol (SIP) is a communication protocol that may be used for a variety of purposes including sending and receiving control signals in a network, for example in a network based on the internet protocol (IP). SIP communication exchanges are based on messages exchanged between entities and that are generally structured as request-response pairs. SIP messages are generally human readable.